EP3191816A1

EP3191816A1 - Process and apparatus for sorting reusable pieces of raw material

Info

Publication number: EP3191816A1
Application number: EP15777613.9A
Authority: EP
Inventors: Edwin BÜCHTER; Winfried Barkhausen; Hans-Bernd Pillkahn
Original assignee: Proassort GmbH
Current assignee: Clean Lasersysteme GmbH
Priority date: 2014-09-11
Filing date: 2015-09-10
Publication date: 2017-07-19
Anticipated expiration: 2035-09-10
Also published as: US20170261437A1; DE102014013160B4; DE102014013160A1; WO2016038153A1; EP3191816B1; US10641712B2

Abstract

The invention relates to a process and an apparatus for sorting reusable pieces of raw material (5), which are continuously moved in a conveying direction (2) by a transporting device (1), wherein an analysis of the chemical composition of the pieces of raw material (5) is performed with the aid of laser-induced plasma spectroscopy (LIBS) and, dependent on the composition determined, an automated sorting of the pieces of raw material (5) is carried out, wherein in a first step the pieces of raw material (5) are subjected to multiple first laser pulses (6), in order to remove surface coatings and/or contaminants from the pieces of raw material (5), and in a second step one or more second laser pulses (7) are directed onto the locations of the pieces of raw material (5) from which the surface coatings and/or contaminants have been removed, wherein exposed material of the pieces of raw material (5) is transformed into a plasma by the second laser pulses (7), wherein the same laser (3) is used for the first and second laser pulses (6, 7) and the area of the pieces of raw material (5) over which the first laser pulses (6) are moved and which are freed of surface coatings and/or contaminants is greater than the area of the pieces of raw material (5) that is exposed to the second laser pulses (7), wherein the focal diameter and the focal point of the laser beam are kept constant between the first and second laser pulses (6, 7). In this way, an unfalsified analysis of the composition of the pieces of raw material (5) can be achieved by using only one laser and, dependent on the analysis, a sorting can be performed.

Description

Method and device for sorting recyclable

raw material pieces

The invention relates to a method for sorting recyclable pieces of raw material, which are moved by a transport device continuously in the conveying direction, wherein an analysis of the chemical composition of the pieces of raw material by means of laser-induced plasma spectroscopy (LIBS) is carried out and depending on the determined composition, an automated sorting of the pieces of raw materials is carried out, wherein the raw material pieces are applied in a first step with a plurality of first laser pulses to remove surface coatings and impurities from the pieces of raw material, and in a second step, one or more further laser pulses are directed to the locations of the raw material pieces on which the surface coatings and / or impurities have been removed, wherein uncovered material of the raw material pieces transferred by the second laser pulses in a plasma and for the first and second laser pulses of the same laser is used. Furthermore, the invention relates to a device for carrying out the method.

In times of scarce and more expensive resources, the recycling of secondary raw materials, for example in the form of scrap recycling, is of considerable economic importance. This is all the more so since large parts of the raw materials used come from third countries, which can not always guarantee security of supply. Finally, the recycling of secondary raw materials is also environmentally desirable. The secondary raw materials are usually present as fractions, which consist of a large number of individual pieces of raw materials. In most cases, the individual fractions do not come from a single point of discharge (place of origin), but are composed of raw materials of different origin. Even the elimination from a certain point of disposal can in turn have different chemical compositions in the individual pieces. Overall, therefore, the individual fractions are usually pre-sorted only in terms of different raw material categories such as affiliation to a base material and the dimension, but often differ significantly in their chemical composition. For example, metal scrap is composed of individual parts of different alloy contents.

For the production of high-performance materials from secondary raw materials, the exact chemical composition of the target melt is of utmost importance in the case of metallic materials. A mere presorting for individual scrap groups may be desirable for the gating, i. Furnace stocking will be sufficient for simpler commodity materials, but not for the production of high performance alloys (HPA) that have particular physical properties in terms of strength, wear and corrosion behavior, heat resistance, conductivity, etc. In addition, so far disturbing alloying elements are still slagged and ultimately destroyed, which in the long term is neither economically nor ecologically acceptable.

As the requirements for materials that are adjusted by macro and micro alloying are getting higher and higher, new alloys with ever finer co-ordinated alloying parts are constantly being produced. However, these alloying constituents may interfere with subsequent recycling, especially if the recycling takes place by melting in induction furnaces that do not allow metallurgical workup. For example, micro-alloying elements, which make up high-strength steel sheet materials, interfere with the indentation of spherical graphite in ferritic basic structure during high-performance iron casting. Therefore, only portions of presorted secondary raw materials from the procurement market for the target melt are usually used. These are then blended with primary raw materials of known composition so that maximum permitted alloy contents are adjusted and, in particular, interfering alloy constituents are pressed below a specified specification limit. In terms of a functioning circular economy but the increase in the secondary raw material content would be desirable.

For this purpose, the secondary raw material pieces must be sorted as accurately as possible in terms of their composition. The sorting requires a prior analysis of the chemical composition, for example, using the laser-induced atomic emission spectroscopy (laser-induced

Plasma spectroscopy; LI BS = laser induced breakdown spectroscopy). A small amount of the material surface to be analyzed is evaporated and transferred into a plasma. The light emitted by the plasma is characteristic of the atomic composition. However, in the LIBS process, ultimately only the surface of the solid is analyzed; the analysis is therefore influenced by surface coatings or contaminants on the surface, so that the measurement result is not representative of the overall composition of the analyzed piece of raw material. In order to solve this problem, for example, DE 44 26 475 A1 proposes to first direct a pulsed laser beam onto the surface layer in order to at least partially remove it, and in a second phase to analyze the exposed material by further laser pulses by means of LIBS. In addition, during the analysis, moving pieces of raw material are to be analyzed by an optical guidance system moving the laser beam synchronously on the measuring point of the moving object, so that the laser pulses are applied to detach the surface coating and analyze the composition to the same location of the piece of raw material. This also has the advantage that can be dispensed with a second laser, which significantly reduces the cost of the overall device.

In this context, it has proved to be problematical that adulteration can occur when the exposed area of the borderline area is exposed Surface a LIBS analysis is performed. In particular with relatively thick coatings, a kind of crater forms on the surface, wherein the crater edge also has elements of the coating or impurities after the action of the laser pulses to detach the surface. If the laser beam intended for the LIBS analysis detects this crater edge, the measurement result does not coincide with the actual composition of the pieces of raw material and it is likely that the result will be incorrect. U. made a wrong assignment. The plasma generated for the LIBS analysis can also be influenced by the crater geometry. To solve this problem, DE 103 61 727 B3 has already proposed to successively reduce the distance of the puncture point of the laser beam axis through the sample surface from the intersection of the focal plane with the laser beam axis in the replacement of the coating and to use a much smaller beam diameter for the actual analysis step. In this way, it is ensured that the analysis pulses only detect the surface of the exposed areas, but do not experience disturbances, for example, in the area of the crater rim.

A disadvantage, however, is noticeable that the variation of the focus diameter requires a relatively complex control of the laser. In addition, a large focus diameter causes poor release of surface layers and a low laser pulse repetition rate, slowing the overall delamination. Accordingly, the overall process is slower, but this is undesirable in view of high throughput rates of pieces of raw material to be sorted. It is therefore an object to provide a method for sorting of recyclable pieces of raw material of the type mentioned, which requires only one laser, effectively removes surface coatings and impurities and performs an analysis of the composition of the pieces of raw material, without the latter by the detached surface coatings / Impurities is corrupted. This object is achieved by methods for sorting recyclable pieces of raw material, which are moved by a transport device continuously in the conveying direction, wherein an analysis of the chemical composition of the pieces of raw material by means of laser-induced plasma spectroscopy (LIBS) and depending on the determined composition of an automated sorting the raw material pieces is carried out, wherein the raw material pieces are acted upon in a first step with a plurality of first laser pulses to remove surface coatings and / or impurities from the pieces of raw material, and in a second step one or more second laser pulses are directed to the locations of the pieces of raw material to where the surface coatings and / or impurities have been removed, wherein exposed material of the raw material pieces is transferred by the second laser pulses into a plasma, wherein for the first u and the surface of the pieces of raw material over which the first laser pulses move and which are freed of surface coatings and / or impurities, is larger than the area of the pieces of raw material detected by the second laser pulses, the focus diameter and the focal point of the laser beam between the first and second laser pulses are kept constant.

According to the invention, an area on the pieces of raw material to be analyzed is exposed by the first laser pulses (cleaning pulses), which area is significantly larger than the area which experiences an action by the second laser pulses (analysis pulses). In this way it is effectively prevented that the analysis pulses detect the crater edge and cause a falsification of the result. It should be ensured that the first laser pulses overlap in such a way that no crater walls are created on the cleaned surface and this receives an adjustable surface fine structure. In addition, it ensures that even with surface layers with particularly high strength for example, several tens to hundreds of microns sufficient laser light reaches the exposed surface and is reflected smoothly from the surface to the detector. The terms first laser pulses and cleaning pulses or second laser pulses and analysis pulses are used synonymously below. As a rule, both the cleaning and the analysis pulses are sequences of laser pulses. As the focus diameter, the diameter of the laser beam in the focal point, ie its thinnest point (beam waist) understood.

In contrast to DE 103 61 727 B3, in which the focus diameter is constantly varied, this is kept constant according to the invention; instead, however, cleaning pulses repeatedly act on closely adjacent locations of the pieces of raw material, so that overall a comparatively large area is uncovered. The cleaning pulses thus "wander" over the raw pieces until a sufficiently large area is sufficiently cleaned for analysis to be available.Overall, the area of the pieces of raw material freed from surface coatings and / or impurities should be at least as large as that of the This area increase should be selected to cover at least one focus diameter and the positional tolerances in the laser beam positioning It is preferred if the surface of the pieces of raw material which is freed of surface coatings and / or impurities, at least four times, preferably at least six times as large as the area of the raw material pieces detected by the analysis pulses.

Depending on the nature and thickness of the surface coatings, it may be necessary to subject the areas to be cleared raw material pieces several times with cleaning pulses. This will ensure that a proper analysis of the composition is then possible. Possibly. a multiple admission can be selected by the user; However, it is also conceivable that the device for carrying out the method according to the invention self-learning recognizes whether a further detachment of surface coatings / impurities is necessary. This can be achieved, for example, by allowing cleaning pulses to act on the surface until the subsequently applied analysis pulses provide a constant result. In this case, the device recognizes its surface texture at multiple changes between first and second laser pulses (cleaning and analysis pulses) at very fast pulse rate and therefore close to each other measuring points along a piece of raw material.

Advantageously, the first laser pulses (cleaning pulses) are guided along at least two dimensions over the surfaces of the pieces of raw material to be liberated from surface coatings / impurities, i. the application is not only punctiform or along a line, but for example in the length (x) and in the width (y) direction. Accordingly, in no dimension is the measurement falsified with the aid of the analysis pulses. By switching between cleaning and analysis pulses (first and second laser pulses), it is possible to use a single laser extremely effectively, even if the pieces of raw material are moved at high speed. To speed up the process contributes in particular that the focus diameter of the laser beam is kept constant, so on the one hand, no complex control between cleaning and analysis pulses is necessary and on the other hand, due to the small focus diameter also in the cleaning pulses effective separation of coatings and impurities. The focus diameter of the laser beam amounts to a few 10 μηπ to a few 100 μηπ, preferably 60 to 140 μηπ.

The emission emanating from transferring a portion of the material of the pieces of raw material into a plasma is directed to a spectrometer, typically via optical fibers. In this case, the spectral emission wholly or partly use the optical path of the laser emission device and coupled by wavelength-selective mirrors or optical elements at a suitable location from the optical beam path of the laser device and fed to the spectrometer. The spectrometer is then followed by a Evaluation of atomic composition. Depending on the composition, the sorting of the piece of raw material to a target fraction or also the sorting out takes place if the piece of raw material proves to be unadaptable or unusable. For each target fraction, certain specifications are made with respect to upper and lower limits of individual components, so that the control unit of the system can each make a decision as to whether a piece of raw material must be assigned to a certain target fraction or to another target fraction.

It makes sense that the control unit ensures the movement-synchronous entrainment of the laser beam in accordance with the movement of the pieces of raw material, as may be the case for example. a. From DE 44 26 475 A1 is known. For this purpose, in particular adjustable deflecting mirrors can be used. The control unit takes into account in particular the movement of the pieces of raw material through the transport device and compensates for the advance of the movement during the processing by the laser device.

Laser pulse durations for the cleaning pulses as well as for the analysis pulses in the range of up to several 100 ns, in particular in the range of 20 to 200 ns, preferably in the range of 60 to 120 ns, have proven to be suitable. In this way, the laser pulses for the different objectives, namely material removal on the one hand and emission spectroscopy on the other hand are suitable.

In principle, however, it is also conceivable that the laser pulse durations for the cleaning pulses are set longer than for the analysis pulses, for example for the cleaning pulses in the range of a few microseconds, for the analysis pulses in the range of a few nanoseconds. This can be achieved by suitable control of the laser with the aid of a Q-switch or Q-switch. The pulse energy between the first and second laser pulses can also be varied in order to use a higher laser energy for the cleaning pulses than for the analysis pulses. However, as described above, it is preferred to keep pulse duration and energy constant between first and second laser pulses. The plasma generated by the second laser pulses is preferably a thermal plasma. Such can be produced by means of solid-state lasers or fiber lasers. For each laser pulse, such a laser shows penetration depths of a few μηπ, which suppresses any surface effects.

The pulse frequency of the analysis pulses and preferably also of the cleaning pulses is typically greater than 10 kHz and is preferably between 20 and several 100 kHz. These pulse rates have proven to be particularly effective for analysis of the composition as well as for cleaning.

The pieces of raw material are expediently moved at high speed, wherein in particular a conveyor belt can be used. In this way, a correspondingly high throughput rate can be ensured, which is necessary for the sorting of large amounts of scrap or other secondary raw material. In addition to the static processing, conveying speeds of the pieces of raw material of> 0.1 m / s, preferably> 2 m / s and in particular of> 3 m / s have proven to be suitable for the method according to the invention. According to the invention, an analysis of the composition of at least a majority of the pieces of raw material and ideally each individual piece should be carried out, so that accurate sorting can be carried out even when mixing fractions of different origin.

The pieces of raw materials are usually primarily secondary commodity pieces, ie pieces of raw material for reuse. However, especially if a particular target composition is to be produced, only or predominantly primary raw material pieces can be added if necessary. As a rule, these are meltable raw materials; ideally, these only have to be melted down in order to obtain a target melt of the desired composition, so that an admixture of other substances or a removal of substances from the melt is no longer or only to a very small extent necessary to produce a new material. In particular, the pieces of raw material may be metal scrap, especially steel scrap, since these make up a considerable proportion of the recyclable raw materials in terms of quantity. In principle, however, the method according to the invention can also be used for other metal scrap, in particular aluminum, copper, zinc and titanium scrap. Particularly useful is the method in the sorting of galvanized steel scrap pieces, since they have a comparatively thick surface coating, which makes an immediate analysis of the composition below the surface coating impossible. It is also conceivable use in the recycling of plastic parts or glass. However, with the aid of the method according to the invention, which combines cleaning pulses and analysis pulses with one another, a targeted analysis and sorting of the steel scrap pieces can also be carried out in this case without the galvanizing leading to a falsification of the results. It is helpful if the raw material pieces are pre-sorted with respect to their basic composition, for example with regard to the base material or the layer system. With known basic composition can be decided whether a treatment of the pieces of raw material with one or more liquids for cleaning the surface and / or the replacement of surface coatings, ie a pickling is necessary before the actual method of the invention is carried out. Here, different approaches may be useful, depending on whether it is z. B. galvanized, enamelled or provided with a plastic coating scrap or plastic remnants. For example, organic solvents such as aliphatic or aromatic hydrocarbons, chlorinated hydrocarbons, alcohols, glycol ethers, dicarboxylic acid esters, acetone, etc. can be used as paint strippers for removing organic coatings. Methylene chloride is used most frequently. To remove a zinc layer, acids or bases can be used. Corresponding methods are known to the person skilled in the art. Particularly effective is a treatment with liquids for cleaning the surface in a vibrating conveyor, as it is the subject of WO 2012/1 10239 A1. To further increase the efficiency, the pieces of raw material to be treated may expediently be mechanically brought into contact with the liquid before being contacted pretreated, in particular comminuted, shredded, roughened and / or otherwise deformed to increase the contact surfaces to the liquid. Possibly. Drying of the pieces treated with the liquid may be carried out prior to the analysis in order to remove adhering liquid residues.

According to a further variant, the first laser pulses are directed to pieces of raw material, which lie farther back in the conveying direction, and the second laser pulses to pieces of raw materials, which have progressed further in the conveying direction, wherein a continuous change between the irradiation of further lying in the conveying direction pieces of raw material with first laser pulses and in Conveying further advanced pieces of raw material with second laser pulses takes place. This may be useful because immediately after exposure to laser pulses to remove surface layers and contaminants, any released material from the coating / contaminant is close to the piece of raw material to be analyzed, which may compromise accurate analysis and result in improper collation. The evaporation of organic surface coatings, oils, fats and varnishes, foreign metal flakes, finishing layers of zinc or tin, oxide layers u. a. can be disturbing here. On the other hand, at least when using only one laser system, which is desirable for cost reasons, no too long waiting time can be built in between the cleaning pulses and the analysis pulses, since with high throughput in the meantime, further pieces of raw material would pass through the LIBS system unanalyzed. The large amount of pieces of material to be analyzed and sorted, which are moved on a conveyor belt at high speed, rather requires the almost continuous use of the laser system.

This can be counteracted by the fact that a control unit ensures that, following the cleaning pulses, the analysis pulses act on another piece of raw material which has progressed further in the conveying direction and in which a detachment of the surface coating with the aid of cleaning pulses of the same laser has taken place shortly before. At the point at which the analysis pulses act on the second piece of raw material, are too At this time no more surface coatings or impurities, because they have been removed in the preceding step by cleaning pulses. Accordingly, an unaltered analysis of the composition is now possible for the second piece of raw material. Of course, the control unit must ensure that the action of the analysis pulses takes place at the same point as the action of the cleaning pulses. This can be achieved by means of a corresponding device of the control unit, which must take into account and evaluate, in particular, the conveying direction and conveying speed of the pieces of raw material and also the steering of the laser pulses. The alignment of the laser beam can be done for example by means of deflecting mirrors.

After the LIBS analysis on the second piece of raw material, the laser beam is again controlled to a piece of raw material, must act at first cleaning pulses to remove surface coatings / impurities on this. Thereafter, a renewed effect of analysis pulses either on the first piece of raw material or another piece of raw material, previously acted on cleaning pulses. The entire process, d. H. the change between the first and second laser pulses is thus clocked constantly repeated. It should be noted, however, that the described change between the individual pieces of raw material in most cases proves unnecessary, since the creation of a correspondingly large area on the pieces of raw material, which is amenable to analysis, falsification by remnants of the detached surface coatings / impurities already be largely excluded. This simplifies the implementation of the method.

Depending on the size of the pieces of raw material, it may be useful to crush them before analysis of the composition in order to make them easier to handle. For a meaningful analysis of the composition is possible, a certain minimum size is required. Since the analysis is often carried out with the aid of a laser having a focal spot of about 50 to 400 μηπ diameter, the minimum size of the individual pieces of raw material should not be less than 2 mm Size, the dimensions in the two dimensions of the support surface, for example on a conveyor belt, are understood, ie the piece of raw material should be at least 2 mm long and wide. Advantageously, the size applies to all dimensions including the height. It is expedient if the individual pieces of raw material are larger, for example, have a size of at least 50 mm, preferably at least 100 mm. On the other hand, the handling of large-scale, thinner pieces of raw material is difficult even in the promotion, which is why the pieces of raw material after a possible crushing step max. should have a size of 2000 mm. Preferably, a max. Size of some 100 mm. If necessary, the comminution step can also be carried out after the step of cleaning or detaching surface coverings.

Before the actual analysis, it may be necessary to separate the raw material pieces in order to be able to analyze the pieces of raw material without hampering the analysis of individual pieces of raw material by other pieces of raw material. The separation of the pieces of raw material can be carried out by conveyor technology in such a way that a plurality of modules are arranged one behind the other, which move the pieces of raw material at different speeds. For example, a first module, the raw material pieces at a relatively low speed of z. B. 5 m / min move. From this module, the pieces of raw material are transferred to another module, the pieces of raw material at a significantly higher speed of z. B. 180 m / min. In this way, the distance between the pieces of raw material is selectively increased, ie there is a separation, which allows the separate analysis. If required, further modules with variable speed can be arranged between the modules with minimum and maximum speed, through which the raw material pieces are moved at medium speeds. A typical speed cascade is about: 5 m / min - 25 m / min - 100 m / min - 180 m / min. If necessary, after separation of the pieces of raw material, the speed can be reduced again in order to carry out the analysis. The modules may be both vibratory conveyors and conveyor belts, typically with the lower speed modules being vibratory conveyors and the higher speed modules being conveyor belts. In particular, the module may have minimum Speed around a vibrating conveyor (vibrating trough or vibrating chute) and at the module at maximum speed around a conveyor belt. The use of vibratory conveyors at the beginning of the separation is also helpful insofar as loosely connected, z. B. easily hooked pieces of raw material can be separated from each other in this way. Possibly. it may be sufficient to carry out the separation only so far that only a few pieces of raw material are present together, ie it is not necessary in each case to make a separation in the sense that all pieces of raw material are completely separated. In order to determine the locations where a spectroscopic analysis of the composition is possible, a determination of the positions of the pieces of raw material as well as a determination of spatial information regarding the pieces of raw material can be carried out. In particular, the partial or complete determination of the shape of the pieces of raw material is understood as the determination of spatial information. The position is in particular the position of the piece of raw material on the transport device.

In order to increase the informative value of the analysis carried out, it is also possible to analyze several sites per composition of a piece of raw material, d. H. It must be done in several places, first an effect of cleaning pulses and then an effect of analysis pulses to determine the particular composition can. The results are statistically evaluated, then sorting is performed depending on the statistically determined composition.

The determination of the position of the pieces of raw material is possible by means of a 3D scanning step, which can also serve to obtain spatial information on the pieces of raw material. It is thus possible to detect the shape of the pieces of raw material. The spatial information on the pieces of raw material, in particular the shape, is automatically evaluated at which positions a spectroscopic analysis is easily possible. In this way, the analysis can be significantly accelerated, since the number of unsuccessful analysis steps is minimized. 3D scanning technologies, usually performed with the help of a laser, are the expert from the prior art and are widely used, for example for the determination of the shape of dental arches, during rapid prototyping, etc. For example only, the review by WR Scott, G. Roth, ACM Computing Surveys, Vol. 35, 2003, Pp. 64-96 "View Planning for Automated Three-Dimensional Object Reconstruction and Inspection".

Instead of capturing position and shape with the help of 3D scanning, other possibilities are conceivable. For example, the position of the piece of raw material in the case of metals can be determined by electromagnetic induction. For this purpose, coils may be provided, for example below the transport device, which together with a capacitor form a resonant circuit, so that the position of a metallic piece of raw material is detected electronically. Devices in which the presence of a metallic object can be detected by means of electromagnetic induction are known in principle to the person skilled in the art.

The extraction of spatial information on the pieces of raw material is also possible by a (pulsed) laser parallel to the transport direction a contour line of each piece of raw material over the light transit time is determined. This serves to prepare the subsequent analysis process in the case of pieces of raw materials which have a considerable height difference in or from piece to piece, so that a light-optical method can focus sufficiently precisely for the actual measurement. The spatial information obtained is used to determine the places where compositional analysis takes place in the subsequent step. By determining the contour line, the cycle time of the measuring processes is increased and the measuring accuracy is increased. In addition, the influence of any relative movements of the pieces of raw material relative to the transport device is largely eliminated by measurement.

In addition to the composition, the sorting process can also take into account the mass of the pieces of raw material in order, as a result, if possible to obtain a target fraction which has the desired target composition as a whole. One speaks in this context of assorting, where an additional weighing process may be required. Such a method is disclosed in DE 10 2012 024 81 6 A1; the process according to the invention can be used in the context of the assorting process described here. The sorting is done by an automated method using a computer or an electronic data processing device. The raw material pieces are sorted into individual target fractions, it also being possible for a residual fraction to be provided in which raw material pieces containing raw materials or material pests that can not be usefully recycled are introduced. Also should be sorted out such pieces of raw materials, which prove to be unanalysable or which are insufficiently prepared or composed of too many different materials pieces such as composites, complete electric motors, or the like.

The sorting can be carried out mechanically or pneumatically by means of conventional methods, for example by continuously conveying scrap metal conveyed via a conveyor belt as required and collecting it in different containers provided. The supply to the target fraction can take place, for example, with the aid of air blasts, as described in DE 100 29 951 A1. However, it is also possible to use mechanical flaps, gripping devices or the like.

When sorting small amounts of alloying components can be considered, which may be preferably below 800 ppm. More preferably, amounts below 500 ppm, in particular below 100 ppm, particularly preferably below 10 ppm, are also included in the analysis and considered for the sorting.

In addition to the method according to the invention, the invention also relates to a device for carrying out the method according to the invention. This device comprises: a laser which is capable of first laser pulses for detaching surface coatings and impurities from pieces of raw material and generate second laser pulses for transferring exposed material of the pieces of raw material into a plasma, a spectrometer for analyzing the light emitted by the plasma, a transport device for moving the pieces of raw material in the conveying direction, a control unit which controls the pulse energy, pulse duration and pulse frequency of the laser and the first laser pulses moved over a surface of the pieces of raw material and freed from surface coatings and / or impurities, which is greater than the area of the pieces of raw material detected by the second laser pulses, and keeps the focus diameter and the focal point of the laser beam constant between the first and second laser pulses, and a sorting unit which automatically sorts the pieces of raw material into one or more target fractions depending on the determined composition.

Incidentally, apply to the device according to the invention all versions including possible embodiments of the invention accordingly.

The invention will be explained in more detail with reference to the attached FIG. This shows a transport device 1, on which a plurality of pieces of raw material 5 in the conveying direction 2 is moved. To simplify the illustration, the raw material pieces 5 are arranged here relatively regularly on the transport device 1, but in practice this is usually not the case. The transport device 1 is a conveyor belt which is driven by rollers 4. At the end of the conveyor belt is a series of collection containers A, B, C, R, in which the pieces of raw material 5, depending on the composition, are collected, then used further to be able to. In this case, the collection containers A, B, C are collection containers for recycling the raw material pieces 5, while the collection container R is a waste collection container in which such pieces of raw material 5 are collected which are not accessible for further use or where no analysis of the composition was possible.

The sorting into the collecting containers A, B, C, R takes place as a function of the determined composition of the pieces of raw material 5. This takes place with the aid of a laser 3 which generates laser pulses, it being necessary to distinguish between cleaning pulses 6 and analysis pulses 7. In each case, cleaning pulses 6 and then analysis pulses 7 act on a specific piece of raw material 5. The control unit ensures that the analysis pulses are directed to the locations of the pieces of raw material 5, on which a material removal by cleaning pulses 6 has previously taken place. For this purpose, the control unit takes into account the position of the raw material pieces 5, the speed of the transport device 1 and the steering of the cleaning pulses 6 and the analysis pulses 7.

Accordingly, a meaningful determination of the composition of the pieces of raw material 5 by means of the analysis pulses 7 is possible. The analysis pulses 7 emanating from the laser 3 transfer parts of the raw material piece 5 into the plasma state, the analysis of the composition takes place with the aid of a spectrometer, not shown here, which captures the light emitted by the plasma. It is thus a LIBS method (laser-induced breakdown spectroscopy); The respective composition of a piece of raw material 5 can be determined from the light captured by the spectrometer. A control unit, likewise not shown here, subsequently ensures that the respective analyzed piece of raw material is assigned to the correct collection container A, B, C, R.

Claims

claims

1 . Method for sorting recyclable pieces of raw material (5), which are moved by a transport device (1) continuously in the conveying direction (2), wherein an analysis of the chemical composition of the pieces of raw material (5) by means of laser-induced plasma spectroscopy (LIBS) and in dependence the determined composition is an automated sorting of the raw material pieces (5) is performed, wherein the raw material pieces (5) are acted upon in a first step with a plurality of first laser pulses (6) to remove surface coatings and / or impurities from the pieces of raw material (5) , and in a second step, one or more second laser pulses (7) are directed to the locations of the pieces of raw material (5) at which the surface coatings and / or impurities have been removed, wherein uncovered material of the pieces of raw material (5) by the second laser pulses ( 7) is transferred into a plasma, wherein for the first un d the second laser pulses (6, 7) the same laser (3) is used,

characterized in that the area of the pieces of raw material (5) over which the first laser pulses (6) move and which are freed of surface coatings and / or impurities, is greater than the area of the pieces of raw material (5) detected by the second laser pulses (7), wherein the focus diameter and the focal point of the laser beam between the first and second laser pulses (6, 7) are kept constant.

2. The method according to claim 1, characterized in that the surface of the pieces of raw material (5), which is freed from surface coatings and / or impurities, at least by the focal diameter and position tolerances is greater than the area of the raw material pieces detected by the second laser pulses (7) (5).

3. The method according to claim 1 or 2, characterized in that the surface coatings and / or impurities to be liberated surfaces of the raw material pieces (5) depending on the nature and thickness of the surface coatings / impurities one or more times from the first laser pulses (6) detected become.

4. The method according to any one of claims 1 to 3, characterized in that the first laser pulses (6) along at least two dimensions over the surface coatings and / or impurities to be liberated surfaces of the raw material pieces (5) are performed.

5. The method according to any one of claims 1 to 4, characterized in that the focus diameter of the laser beam is between 60 and 140 μηπ.

6. The method according to any one of claims 1 to 5, characterized in that the pulse length of the first and second laser pulses (6, 7) 20th

- 200 ns and preferably 60 - 120 ns.

7. The method according to any one of claims 1 to 6, characterized in that the plasma generated by the second laser pulses (7) is a thermal plasma.

8. The method according to any one of claims 1 to 7, characterized in that the laser (3) is a solid-state laser.

9. The method according to any one of claims 1 to 8, characterized in that the laser is a fiber laser.

10. The method according to any one of claims 1 to 9, characterized in that the raw material pieces (5) at a speed of> 0.1 m / s, preferably> 2 m / s are moved in the conveying direction.

1 1. Method according to one of claims 1 to 10, characterized in that the raw material pieces (5) are steel scrap pieces.

12. The method according to claim 1 1, characterized in that the steel scrap pieces are galvanized steel scrap pieces.

13. The method according to claim 1 1, characterized in that it is the pieces of raw material (5) to non-ferrous metal scrap pieces.

14. The method according to any one of claims 1 to 13, characterized in that the first laser pulses (6) are directed to pieces of raw material (5) which lie further back in the conveying direction (2), and the second laser pulses (7) on pieces of raw material (5) directed, which are further advanced in the conveying direction (2), wherein a continuous change between the application of further in the conveying direction (2) pieces of raw material (5) with first laser pulses (6) and in the conveying direction (2) further advanced pieces of raw material (5) takes place with second laser pulses (7).

15. Apparatus for carrying out a method according to one of

Claims 1 to 14 with a laser (3) which is capable of first laser pulses (6) for detaching surface coatings and impurities from pieces of raw material (5) and second laser pulses (7) for transferring exposed material of the pieces of raw material (5) to generate a plasma, a spectrometer for analyzing the light emitted by the plasma, a transport device (1) for moving the pieces of raw material (5) in the conveying direction (2), a control unit which controls the pulse energy, pulse duration and pulse frequency of the laser (3) and moves the first laser pulses (6) over a surface of the pieces of raw material (5) and freed of surface coatings and / or impurities greater than the area of the pieces of raw material (5) detected by the second laser pulses (7), and the focal diameter and the focal point of the laser beam between the first and second laser pulses (6, 7) constant holds, and a sorting unit, the pieces of raw material (5) automatically sorted depending on the determined composition of one or more target fractions.